Survival of the Fittest is Not Related to Physical Fitness

Almost everyone has heard of evolution and most of us have a vague idea of what it means. Animals with useful traits survive and pass on their genes. Over time, these positive traits become more common and a species evolves. Most of us aren’t scientists, though, and a number of evolution myths have popped up over time.

Myth #1: Evolution is “just” a theory

We usually think of theories as being possibilities, not facts. A “theory” in science, though, takes on a different meaning. I personally like this definition from the National Academy of Sciences:

“a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses”

In other words, a scientific theory is an explanation that has been backed up by many studies and a substantial amount of evidence. We don’t call it a “fact” because science can always change as we learn new information. We’re all pretty sure the Earth rotates around the Sun yet that concept is called the heliocentric theory. It’s pretty unlikely we’ll find any evidence that goes against this “theory” but scientists still don’t call it a fact.

Myth #2: Humans evolved from monkeys

This is a common one and often used in an attempt to discredit evolutionary theories. It’s also not true; humans did not evolve from monkeys. We did share an ancestor with African apes (note that “apes” aren’t monkeys) about 8 million years ago but that doesn’t mean we evolved from them. Instead, there was a great ancestor that eventually gave rise to humans and apes. We’re most closely related to chimpanzees because of this ancestor but there were two distinct evolutionary paths.

When the human species began to evolve, the chimpanzee species was evolving separately. We’re related, we didn’t directly evolve from any modern primate species. We do share over 90% of our DNA with non-human primates, including gorillas and other great apes. On the other hand, humans also share 90% of their DNA with mice! That doesn’t mean humans evolved from mice, it’s just a result of most mammals sharing genes.

Myth #3: Survival of the fittest means the strongest will survive

Sometimes people will use the term “survival of the fittest” to excuse a behavior. I’ve unfortunately overheard someone say that we shouldn’t help those weaker than us because “it’s survival of the fittest!” The average person interprets this idea, originally thought up by Charles Darwin, as meaning that the very strongest will survive. The problem is that “fitness” has an entirely different meaning in biology. It doesn’t refer to strength, health, or physical fitness at all. Instead, biological “fitness” refers to the ability to pass on your genes, generally by having offspring.

In evolution, the end goal is to pass on your genes to the next generation. That doesn’t necessarily require being the strongest, however. In fact, animals that get into too many fights might become injured or killed. Even if they won most of those fights and were the strongest in their group, death means they won’t be passing on their genes. Those animals would therefore be considered to have low fitness. On the other hand, a somewhat weaker animal that stays out of danger might be able to successfully raise several offspring. That animal would be said to have high fitness. In primates, including humans, being a good parent will often raise fitness more than being strong. From an evolutionary standpoint, being able to lift heavy weights means nothing if you never settle down and raise children.

If you want to learn more about how evolution works, the University of California in Berkeley (among others) have put together great evolution resources: click here.